The dynamic range of the camera is always the same for each ISO setting, and it drops by approximately a stop for each stop of ISO increase. However the contrast range of each photo you take IS dependent on exposure time. You may not necessarily use the full dynamic range offered by your camera in each and every shot. If you are not saturating your photos, which means exposing to the point of nearly over-exposing, then you can probably expose longer to utilize more of the dynamic range offered by the camera.
–
jrista♦Sep 9 '12 at 17:39

2 Answers
2

The most significant factor that affects dynamic-range captured by the sensor is ISO. The higher the ISO, the lower the dynamic range. So to maximize dynamic-range you have to shoot at the native ISO of your camera. Longer exposures can add very slightly more noise as the sensor heats up but if you compare this to the loss of dynamic-range from using a higher ISO, it is completely insignificant.

Camera settings affect the dynamic-range of JPEG images. Most modern cameras have a highlight priority option which lets them store more dynamic range when producing a JPEG. Color modes or picture styles also affect this. The modes with the least contrast such as Natural or Faithful, show the most scene dynamic range.

Dynamic range is independent of exposure time and settings. Regardless of whether you take a shot at f/16 for 1/60th or f/8 for 1/125th (for example), if the dynamic range is too large for your sensor to cope with, some part of your shot will be exposed incorrectly.

A scene with large dynamic range essentially requires two different exposures in the same shot: a longer exposure for the darker part and a shorter exposure for the lighter part.